Flow control for compressors and pumps

ABSTRACT

This flow control comprises a vane equipped guide element disposed in a fluid compressor or pump between the usual impeller and the fluid inlet. The element is mounted for rotation either by fluid drawn into the inlet by the impeller or by a positive displacement fluid energy transfer member connected with the element and communicating with a fluid system external of the compressor. Valve and pump means may be utilized in the fluid system to control the operation of the guide element. If desired, the guide element may be permitted to windmill freely in response to flow of fluid into the compressor, it may also be held stationary, or it may be driven by an external force in a selected direction at a controlled speed to secure the desired effect. The vanes on the element direct the inflowing fluid to the impeller in a manner to improve the performance of the compressor or pump.

United States Patent Kumm 1541 FLOW CONTROL FOR COMPRESSORS AND PUMPS [76] Inventor: Emerson L. Kumm, 1035 E. Laguna Drive. Tempe. Ariz. 85282 [22 Filed: Sept. 5, 1974 [21] Appl. No.: 503,469

[52] US. Cl. i. 415/61; 415/62; 415/143 [51] Int. C15 ..F01D1/24 [58] Field of Search 415/60, 61, 62, 66 67, 415/68, 143. 147

[56] References Cited UNITED STATES PATENTS 2400.241) 5/1946 Lincoln 415/62 23 5531 6/1951 Bollay v i 415/143 3.5461180 12/1971) Schwaar 415/62 2 692.4 1] 9/1972 Mittelstaedt 415/143 FOREIGN PATENTS OR APPLICATIONS 963.415 1/1951) France 415/62 399.619 10/1933 United Kingdommu 521L541 2/1952 Canada .i 415/62 Primary ExaminerHenry F. Raduazo Attorney: Agenl. or Firm-Herschel C. Omohundro [57] ABSTRACT This flow control comprises a vane equipped guide element disposed in a fluid compressor or pump between the usual impeller and the fluid inlet. The element is mounted for rotation either by fluid drawn into the inlet by the impeller or by a positive displacement fluid energy transfer member connected with the element and communicating with a fluid system external of the compressor. Valve and pump means may be utilized in the fluid system to control the operation of the guide element. If desired. the guide element may be permitted 'to windmill freely in response to flow of fluid into the compressor. it may also be held stationary, or it may be driven by an external force in a selected direction at a controlled speed to secure the desired effect. The vanes on the element direct the inflowing fluid to the impeller in a manner to improve the performance of the compressor or pump.

7 Claims, 7 Drawing Figures Sheet 2 of2 3,918,828

DESIGN- omr:

6 50 0-5.6 REES 6* 5 8.5 DEG.

Vu=500 FT/ SC.

FT/SC.

/ FT/SC WEIGHT FLOW RATIO.

FRACTION OF MAXIMUM p/w F'GOS. I

400 I FT/SC.

Wp/W /0.5

FT/SC] 40 6 DEGREES FIG. 5.

50 DEGREES 0.7 WEIGHT FLOW RATIO, FRACTION OF MAXIMUM DESIGN POINT a: 5zr=as50ee US. Patent Nov. 11, 1975 m w m w 898% 5 a O (0 P300 U.

FLOW CONTROL FOR COMPRESSORS AND PUMPS BACKGROUND OF THE INVENTION This invention relates generally to fluid moving apparatus. such as compressors or pumps, and is more particularly directed to means in such apparatus for controlling flow of fluid therein to improve the efficiency thereof.

The invention relates to the class of structure exemplified by the following patents:

l.46l).42l Moody. I.. F. l.578.843 Moody, l.. F. 2.306.742 Moody. I.. F. 2.56l.84() Busquet. .I. C. 2.733.853 Trumpler. W. E. 3.289.9l) Wood. G. R. 3.657.881 Amman. C. A.. ct. al. 3.724.208 Welch. E. 8.. ct. al.

SUMMARY OF THE INVENTION An object of this invention is to provide a compressor or pump of the type having an impeller, which draws fluid into a casing and expels it therefrom, with means upstream of the impeller for guiding the fluid to the impeller in a manner to improve the operation and efficiency of the device. It has been found in some instances where pumps or compressors are driven at relatively constant speed that it is desirable to vary the output to meet certain conditions. Heretofore, this objective has been accomplished, without complete satisfaction, either by throttling the discharge with its attending power losses, or by limiting the intake or flow through the use of expensive and complicated controls such as adjustable inlet guide vanes with their inherent losses by leakage, their requirements of gearing and difficulties of operation. It is an object herein to secure the flow control in a unique inexpensive manner.

Another object of the invention is to provide a compressor or pump with flow control means having an inlet guide which may be supported for rotation in the compressor or pump and permitted to windmill, be held stationary or driven at suitable speeds in forward or reverse directions;

Still another object of the invention is to provide a compressor or pump, of the type having a centrifugal impeller, with fluid guide means between the impeller and the compressor inlet, the guide means having a vaned element supported for rotation and means for controlling the speed and directions of rotation of such element.

A further object of the invention is to provide the guide means referred to in the preceding paragraph with a shaft and a fluid pressure energy translating device connected therewith. the latter being arranged in a fluid system operative to transmitenergy to or absorb energy from the guide means.

Still another object of the invention is to provide the guide means with a vane construction which will direct fluid flow in the most effective manner.

A further object is to provide the fluid guide means mentioned in several of the preceding paragraphs with flow splitting means between the outer ends of the vanes and the guide hub, the flow splitting means being shaped to obtain the desired velocity and direction profile from hub to tip ahead of the impeller.

2 Other objects and advantages of the invention will be obvious from a perusal of the following description of one form of the invention which has been shown in detail in the accompanying drawings.

IN THE DRAWINGS FIG. 1 is an axial sectional view, partly schematic, of a compressor equipped with a flow control means embodying the invention;

FIG. 2 is a fragmentary sectional view taken through the guide and impeller on the line IIII of FIG. 1 to show the relationship of the blades on these two elements;

FIG. 3 is a perspective view of a portion of the flow control means shown in FIG. 1;

FIG. 4 is a view showing the entrance end ofthe compressor impeller and one vane of the flow control rotor with appropriate velocity triangles. well known to those skilled in the art, to illustrate the theory of incompressible fluid flow through a compressor embodying the invention;

FIG. 5 is a graph with curves showing the derived angle relationship for the exit angle of a blade on the guide member versus the inlet angle of a blade on the impeller minus the desired angle of attack;

FIG. 6 is a graph with curves showing how the vaned rotary element power loss varies with the reduction weight flow caused by changing the speed of the vaned rotary element used with an air compressing impeller;

and

FIG. 7 is a graph with curves showing the vaned rotary element speed as a function of the weight flow ratio for a specific rotary vane and impeller design.

DESCRIPTION OF THE DISCLOSURE Referring more particularly to the drawings and especially to FIGS. 1 and 2, it will be apparent that the invention has been illustrated as applied to a centrifugal pump or compressor 10. The latter has a casing 11 with walls 12 and 13 spaced to provide an annular inlet 14, a rotor chamber 15, and a radially outwardly extending annular outlet 16, the latter being provided with the usual diffuser vanes 17.

Within the chamber 15 there is'supported for rotary movement the usual impeller 18 of the centrifugal type having a hub 19, curved blades 20, and a drive shaft 21 through which the impeller is driven by a prime mover (not shown). The blades are substantially conventional. having axially facing leading'edges 22, and radially facing trailing edges 23. The hub is curved. as at 24, to turn the fluid being pumped from an axial direction to a radial direction as it flows through the passages between the blades. From the short description of the compressor thus given it will be obvious that when the shaft 21 is driven in the proper direction, fluid will be drawn into the chamber 15 via the inlet 14 and expelled through the outlet. In such flow, without other structure, the fluid changes direction from radially inwardly in the inlet to axially through the chamber 15 to the leading edges of the impeller blades after which it is whirled and turned in the impeller to flow outwardly through the outlet 16. In the latter, diffuser vanes convert the velocity to pressure. As mentioned. the operation thus far is substantially conventional.

In many prior constructions. guide means are providedupstream of the impeller to initially impart whirl to the fluid immediately prior to its entry into the impeller passages. In some prior constructions the guide means are made adjustable to secure varied results. Frequently the mechanism for accomplishing such adjustment is complicated and inefficient in operation and otherwise objectionable.

To avoid the foregoing objections and secure other additional advantages, the flow control means of the present invention. designated generally by the numeral 25, has been provided. The flow control means includes a rotary guide member 26 fixed on one end of a shaft 27 supported for rotation in bearing 28 at the outer end of and in alignment with the axis of the impeller. The guide member 26 includes a hub 29 and radially outwardly projecting blades 30. As shown in FIGS. 2, 3 and 4, blades 30 curve backwardly and laterally from the forward or leading edges 31 to the rear or trailing edges 32. The blades 30 may also taper in thickness from the leading to trailing edges. The lateral direction of curvature of the blades 30 is opposite to that of the impeller blades, as will be apparent from FIGS. 2 and 4. From FIG. 4 it will be noted that the exit angle of the blades of the guide, i.e., the angle of the blade relative to the plane of rotation, is between 30 and 60 degrees. From the same Figure it will also be noted that the entrance angle of the blade of the'impeller with which the disclosed guide means is used is approximately 45 degrees to the plane of rotation, the direction of rotation of the impeller being opposite to that of the guide when the latter is driven by fluid flowing into the compressor. The blades 30 are reinforced by thin webs 33 extending between adjacent blades and such webs combine to form a frustoconical tube between the hub 29 and the peripheral ends of the blades, the base of the frustum facing toward the inlet of the compressor. in addition to reinforcing the guide blades 30, this tube also serves to modify the radial fluid velocity profile at the impeller inlet.

As shown in FIG. 1, the outer end of the shaft 27 is provided with one element 34 ofa fluid energy translating device such as a positive displacement pump or motor designated generally by the numeral 35. This device includes a casing 36 with combination inlet-outlet ports 37,38 which communicate with a fluid pressure.

system 39. System 39 may be provided with another pump 40, a valve 41,,and a reservoir 42. Through the adjustment of valve 41, pump or motor may be caused to impose a load (constant or variable, as desired) on the rotary guide member 26 to govern its speed of rotation and effectiveness asa flow control for the compressor. The pump 40 may be driven, if desired, to drive pump or motor 35 (in either desired direction) and impart rotary movement to guide member 26 to create a desired flow control effect.

From the foregoing it will be recognized that means have been provided for controlling the output of a fluid pump or compressor by varying the fluid flow into the impeller or other fluid motivating means. Such flow controlling means includes a guide element of a rotary type with vanes or blades and other means for modifying the direction and speed of flow of fluid entering the pump or compressor. The flow controlling means also includes a fluid pressure energy translating device disposed in a fluid pressure system with means for loading the fluid pressure energy translating device to control the speed and direction of rotation of the guide element and additional means for causing the guide element to revolve in a desired direction and at a predetermined speed. The guide element has vanes or blades shaped to change the axial flow to a flow containing a whirl velocity most suitable for flow control from the pump or vanes 30 of the guide element 25. Accordingly, V,. will.

then represent the fluid velocity relative to the pump or compressor impeller blade 20. The axial fluid velocity is then represented by V,,. The velocity ofthe vaned rotary guide element blade is represented by U,. lower vector diagram with the magnitude and direction of fluid velocity V the same as in the upper vector diagram. The velocity of the fluid at the trailing edge of the vaned rotary guide element blade 301relative to. such blades is then represented by V .The trailing or exit angle of the blade 30 of the guide element and the inlet angle of the pump or compressor blade, specify the blade geometry significant to the embodied construction. An angle of attack, is designated as used in:

a well-known fashion by designers of turbomachinery blade elements. lo the upper vector diagram, the as.-

sumed velocity and angular relationship result in'a pre whirl fluid velocity of V,, which extends in the same direction as the pump or compressor blade velocity U For efflcient pump or compressor performance,,it is necessary that the angle not vary by more than 3 to 5 in either direction for efficient operation, as is well known in the design of turbomachinery blade elements. As will be shown, this fact then requires a prescribed relationship between rotating elements 18 and 25 and the axial flow velocity V,,.

Assume, in a first case. that the vaned rotary element 25 is substantially unrestricted in its rotation and windmills freely in the fluid flow. [t is observed thatthe fluid flow direction will be substantially unchanged in pass ing through the vaned rotary element blades 30, and consequently give a prewhirl velocity, V,,, that is very small. Assume, now in a second case, that the vaned rotary element 25 is held stationary, such as by closure of valve 41 to prevent flow from pump 35 which is connected with such element, the fluid flow direction as it passes through the vaned rotary element blades 30 will be substantially changed and will give a large value to the prewhirl velocity V,,. Now, it may be seen that to maintain the same, or nearly the same, value of the flow angle, it is necessary that the axial flow velocity, V,,. be greatly reduced compared to that of the first case.

Thus, it is perceived that the most efficient axial flow I velocity, V will decrease as the vaned rotary element velocity, U,., is decreased from its free windmilling speed to a lower velocity approaching that of a stationary vaned rotary element. The mass flow for incompressible fluid is directly proportional to the axial flow velocity, V,,. Hence, it is shown that decreasing the speed of the vaned rotary element corresponds to reducing the mass flow to the impeller of the compressor or pump for most efficient operation.

Using the velocity triangles of FIG. 4, the geometrical design angle, may be specified relative to the exit angle, of the blade 30 of the rotary element 25 and the weight flow ratio limit as given on FIG. 5. The weight flow ratio limit, p/W. is defined as the ratio of the inlet weight flow with a stationary vaned rotary element 25 to the inlet weight flow with a freely windmilling vaned in the This equation is derived as follows: By continuity of flow 1. w A V, With prewhirl tan tan n/l r i-l 3 V,, [L,. V,,} tan Let E (2 Eq" (3 (U,. V,,) tan (U,. V,,) tan Solve for V,,,

V,. ltan tan ()1 U,. tan U,. tan V,,= [U tan U tan l/[tan tan ()1 Sub. in Eq" (1) and (2) U. tan U. tan (4) W,,=A U tan tan tan

[U,. tan I U,. tan

[tan I tan W,, U,. tan

W U, tan

Note that from Eq" (2) (7) tan V,./V..= um

Eq" (6) may be simplified to i u /uq/l: tan (65 1 tan The hydraulic oil pump 35, shown in FIG. 1, may be operated as a motor by a pressurization of the oil through the operation of pump 40 to cause the vaned rotary element to rotate at speeds greater than the free windmilling speed. It may be seen that such rotation would increase the inlet weight flow to more than that obtained with the freely rotating windmilling element 25. Also. the hydraulic pump or motor 35 could be operated in a reverse direction by suitable pressurization of the system 39 with pump 40. This action would cause the element 25 to rotate in a reverse direction and decrease the inlet weight flow in comparison to that resulting from a stationary vaned rotary element.

6 With an impeller having the same value of as before. the same efficiency of impeller operation would result. Using the well-known Euler energy loss equation.

tan

tang tan the theoretical power loss may be computed for a specific design. FIG. 6 gives such power loss by a vaned rotary element 25 using air at various flow velocities. V,, over a flow ratio range achieved by changing the vaned rotary element speed. U... for a construction using 50 and 38.5. The horsepower loss equation for one pound per second flow is:

Ian

FIG. 7 shows how the vaned rotary element speed changes with weight flow reduction in order to hold constant.

From the foregoing description of the construction and theory of operation, it is evident that control of the speed of the vaned rotary element mey be used to rapidly and efficiently change the mass flow through a compressor or pump impeller which is operating at a relatively constant speed. As previously pointed out, the valve 41 and switch 42. or other controls for the motor of pump 40, may be remotely located and integrated as desired into an overall control system.

I claim:

1. Flow control means for compressors and pumps of the type having a casing with an inlet, an outlet, and an impeller supported for rotation between said inlet and outlet to draw fluid into said inlet and discharge it from said outlet, said flow control means comprising:

a. guide means mounted in the casing between said impeller and the inlet, said guide means being supported for rotary movement and having vanes engaged by fluid flowing to said impeller to impart direction to such fluid; and

b. fluid pressure responsive means disposed exteriorly of said casing for controlling the rotary movement of said guide means to obtain a predetermined speed ratio range relative to said impeller.

2. The flow control means of claim 1 in which the guide means has an annular collar between the ends of the vanes and the hub. said collar being conical with the base of the cone facing toward the casing inlet.

3. The flow control means of claim 1 in which the means for controlling the rotary movement of said guide means has a fluid pressure energy transfer system associated therewith.

4. The flow control means of claim 3 in which the fluid pressure energy transfer system has a reversible fluid pump connected for rotation with the guide means and means for controlling fluid flow to and from the pump.

5. The flow control means of claim 4 in which the re versible fluid pump is of the positive displacement type and the fluid flow control means has a selectively operable valve.

6. The flow control means ofclaim 1 in which the impeller of the compressor is a centrifugal type and the guide means has a hub in axial registration with the impeller, vanes extending radially outwardly from the 7 hub. said vanes being curved from the leading to trailing edges with the exit angle between thirty and siiity degrees. a flow guide collar extending from the leading I end of said shaft. and a fluid system communicating with said fluid energy transferring means.

7. The flow control means of claim 6 in which the fluid system communicating withsaid fluid energy transferring means has a valve for governing flow to and from said energy transferring means and means for moving fluid under pressure to said fluid energy transferring means.

Patent No. 3,918,828 D t d November 11, 1975 Page 1 of 4 Inventor(s) Emerson L. Kumm It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, Line 20, 21'

and 4. From FIG. 4 it will be noted that the exit angle, 6 of the blades of the guide, i.e. the angle of the blade Column 4, Line 14 tary guide element blade is represented -by U in the Column 4, Line 20, 21

exit angle, 9 of the blade 30 of the guide element and the inlet angle, of the pump or compressor blade, specify Column 4, Line 23 struction. An angle of attack, X is designated as used in Column 4, Line 30, 31

necessary that the angle, @-5 not vary by more than 3 to 5 degrees in either direction for efficient operation, as is well Column 4, Line 50 angle, 8 X it is necessary that the axial flow velocity, V

Column 4, Line 63, 64

design angle, --K may be specified relative to the exit angle, 9 of the blade 30 of the rotary element 25 and the Column 4, Line 66 flow ratio limit, W /W, is defined as the ratio of the inlet Column 5, Line 6-10 Patent No. 3,918,828 Dated November 11, 1975 InVentOr(S) Emerson L. Kumm Page 2 of 4 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, Line 13-30 (1) N (3A V with prewhirl tan 9 V /(U V (2) V (U V tane V tzn- U tan (Q-X) V7, [U VP] (3) v [11 Vp]tan (3-3 Let Eq (2) Eq (U VP) tame (U VP) tan 4) Solve for V V [tang tan (6-10] U tan -1!) U tan 9 Sub, in Eq (1) and (2) v [u tan ((3%) u tan9]/E:an9 n 401 tan 9 If Vp 0, zero prewhirl Q Patent No. 3,918,828 Dated November 11, 1975 Inventor(s) Emerson L. Kumm ge 3 0f 4 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, Line SO -55 By E (2), v UV tan@ 0 y q 1 tan (5) W f'AV QAU tan ((5--}(), Constant angle of attack.

Dividing (4) by (5) 0 [1 U tan9 tan 9 m) (6) w /w [U /11 tan ((54) 1+ tag (6%) Note that from Eq (2) (7) tanol. =v/'v 1 -U/V p a tan 6 V a Eq (6) may be simplified to Q (8) w /w [1 U /U J/Ll W] UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,918,828 Dated November 11, 1975 Inventor(s) Emerson L. Kumm Page 4 Of 4 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, Line 1 with an impeller having the same value of G- X as before Column 6, Line 4-8 2 tanOL 2 :l E V tan 0L L [tanQ Column 6, Line l3, l4

Rotary element speed, U for a construction using 6 50 degrees and 5- X= 38.5 degrees. The horsepower loss equation for one Column 6, Line 16-20 Column 6, Line 22 Changes with weight flow reduction in order to hold -K Column 6, Line 30 the valve 41 and switch 42 or other controls for the Signed and Sealed this A nest:

RUTH C. MASON .-llu'sling Officer C. MARSHALL DANN (nmmissz'vm'r qflarunls and Trademarks 

1. Flow control means for compressors and pumps of the type having a casing with an inlet, an outlet, and an impeller supported for rotation between said inlet and outlet to draw fluid into said inlet and discharge it from said outlet, said flow control means comprising: a. guide means mounted in the casing between said impeller and the inlet, said guide means being supported for rotary movement and having vanes engaged by fluid flowing to said impeller to impart direction to such fluid; and b. fluid pressure responsive means disposed exteriorly of said casing for controlling the rotary movement of said guide means to obtain a predetermined speed ratio range relative to said impeller.
 2. The flow control means of claim 1 in which the guide means has an annular collar between the ends of the vanes and the hub, said collar being conical with the base of the cone facing toward the casing inlet.
 3. The flow control means of claim 1 in which the means for controlling the rotary movement of said guide means has a fluid pressure energy transfer system associated therewith.
 4. The flow control means of claim 3 in which the fluid pressure energy transfer system has a reversible fluid pump connected for rotation with the guide means and means for controlling fluid flow to and from the pump.
 5. The flow control means of claim 4 in which the reversible fluid pump is of the positive displacement type and the fluid flow control means has a selectively operable valve.
 6. The flow control means of claim 1 in which the impeller of the compressor is a centrifugal type and the guide means has a hub in axial registration with the impeller, vanes extending radially outwardly from the hub, said vanes being curved from the leading to trailing edges with the exit angle between thirty and sixty degrees, a flow guide collar extending from the leading to the trailing edges of said vanes between the ends of said vanes and said hub, said collar decreasing in diameter between the leading and trailing edges of said vanes, the means for controlling rotary movement of said guide means having a shaft projecting forwardly from said hub, fluid energy transferring means at the end of said shaft, and a fluid system communicating with said fluid energy transferring means.
 7. The flow control means of claim 6 in which the fluid system communicating with said fluid energy transferring means has a valve for governing flow to and from said energy transferring means and means for moving fluid under pressure to said fluid energy transferring means. 